Modulation of inflammation by vitamin E and C supplementation prior to anterior cruciate ligament surgery

Abstract

Muscle atrophy commonly follows anterior cruciate ligament (ACL) injury and surgery. Proinflammatory cytokines can induce and exacerbate oxidative stress, potentiating muscle atrophy. The purpose of this study was to evaluate the influence of prior antioxidant (AO) supplementation on circulating cytokines following ACL surgery. A randomized, double-blind, placebo-controlled trial was conducted in men undergoing ACL surgery, who were randomly assigned to either: (1) AO (200 IU of vitamin E (50% d-alpha-tocopheryl acetate and 50% d-α-tocopherol) and 500 mg ascorbic acid), or (2) matching placebos (PL). Subjects took supplements twice daily for 2 weeks prior to and up to 12 weeks after surgery. Each subject provided five blood samples: (1) baseline (Bsl, prior to supplementation and ∼2 weeks prior to surgery), (2) presurgery (Pre), (3) 90 min, (4) 72 h, and (5) 7 days postsurgery. Following surgery, inflammation and muscle damage increased in both groups, as assessed by increased circulating IL-6, C-reactive protein, and creatine kinase. During AO supplementation, plasma α-T and AA increased while γ-T concentrations decreased significantly (P <  0.05). At 90 min the AO group displayed a significant decrease in AA, an inverse correlation between AA and (interleukin) IL-8 (r² =  0.50, P <  0.05), and a significantly lower IL-10 response than that of the PL group. IL-10 was significantly elevated at 90 min and 72 h in the PL group. In summary, our findings show that circulating inflammatory cytokines increase and AO supplementation attenuated the increase in IL-10 in patients post-ACL surgery.

Introduction

The anterior cruciate ligament (ACL) is one of four major ligaments in the knee that provides stability and strength to the knee joint. Immediate (i.e., 1 week post-ACL surgery) and persistent (i.e., months to years) leg muscle atrophy commonly follows an ACL injury and surgery [1], [2], [3], [4], [5]. Increases in both circulating oxidative stress markers [6], [7] and synovial fluid proinflammatory cytokines [8] have been observed following ACL surgery. Importantly, proinflammatory cytokines induce oxidative and nitrative stress [9], [10] and mediate muscle atrophy or proteolysis [11], [12], [13], [14].

Following acute disease, trauma, ischemia–reperfusion injury, or limb remobilization, the induction of a inflammatory cytokine cascade may initiate both circulating and local inflammatory responses [15]. Proinflammatory cytokines (i.e., TNF-α, IFN-γ, interleukin (IL)-1β) promote inflammation, whereas anti-inflammatory cytokines (i.e., IL-4, IL-5, IL-10, and IL-13) are up-regulated by and suppress the activity of proinflammatory cytokines [15].

The inflammatory response may lead to muscle atrophy. Elevated circulating proinflammatory cytokines are related to decreased muscle mass in a variety of human conditions (i.e., aging, COPD, heart failure, etc.) [16], [17], [18]. Other evidence supports the observation that proinflammatory cytokines induce muscle atrophy [11], which may be mediated in part by oxidative stress [12].

The regulation of inflammation is an active area of investigation. Anti-inflammatory cytokines provide endogenous protection against proinflammatory cytokines. Moreover, there are adverse consequences to taking anti-inflammatory medications [19]. Oral antioxidant (AO) supplementation is an attractive therapeutic alternative because AO may be able to ameliorate the increase in proinflammatory cytokines and the deleterious processes that they potentiate.

Vitamins E (α-tocopherol (α-T)) and C (ascorbic acid (AA)) are two of the major dietary AO that ameliorate oxidative stress [20], [21]. Oxidative stress is commonly described as the overproduction (relative to the level of antioxidants) of reactive oxygen (ROS) and nitrogen species (RNS) that elicit protein, lipid, and nucleic acid damage [22]. Vitamin E supplementation also attenuates the elevation in proinflammatory cytokines in humans [23], [24], [25] while minimizing muscle atrophy following limb immobilization [26] and hindlimb suspension [27] in experimental animal studies. Vitamin C recycles vitamin E [28], [29] and is highly concentrated in neutrophils which aids in the protection against the inflammatory-derived respiratory burst [30]. In addition, vitamin C possesses the ability to reduce the secretion of an anti-inflammatory cytokine (i.e., IL-10) from isolated human peripheral blood mononuclear cells [31].

We hypothesized that AO supplementation prior to ACL surgery would attenuate the increase in inflammatory cytokines. Therefore, the purpose of this study was to evaluate the influence of combined vitamin E and C supplementation on the circulating inflammatory cytokine response following ACL reconstructive surgery.